How to Read a Datasheet
Prepared for the WIMS outreach program
5/6/02, D. Grover
In order to use a PIC microcontroller, a flip-flop, a photodetector, or
practically any electronic device, you need to consult a datasheet. This is the
document that the manufacturer provides telling you
• the typical device performance
• minimum and maximum requirements and characteristics
• what you can do to the device without harming it
• suggested uses and hints
Manufacturers want you, the designer, to have a successful experience with
their device. They are trying to be helpful. They don’t always succeed. The
datasheet on the following pages is a relatively good datasheet. It tries to
concisely tell you everything you need to know about the device, a common
555 timer chip (the duct-tape of the electronics hobbyist). Most datasheets
for ICs follow the same general layout.
You don’t have to understand everything in a datasheet. There’s a lot of
information that might not be of any use to you. The annotations that follow
try to point out parts of the datasheet that you should pay particular attention
to.
Where do you find datasheets? Nowadays you can find almost any
datasheet on the internet, often in PDF (Acrobat) form. For example, the
LM555 datasheet from National Semiconductor is on their website at
www.national.com.
What is the LM555? The LM555 is a timer chip that uses external resistors
and capacitors to generate either a single pulse of a certain duration, or a
continuous sequence of pulses with a variety of pulse widths possible.
Because it is a very general purpose collection of functional blocks such as
comparators, a flip-flop, internal voltage divider, high power output stage,
and so on, a number of different timing-related functions are possible.
Entire books have been written about the 555, though it is often used when
another IC would work better. (See for example the CD4538 timer chip.)
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